In the field of microwaves and millimeter waves, a passive device constituted by a post-wall waveguide (PWW) is used. Examples of such a passive device include a directional coupler and a diplexer. A terminator constituted by any of such passive devices and having a termination function added to the passive device has conventionally been known.
In connection with the terminator, for example, Patent Literature 1 discloses an arrangement in which termination is performed inside a post-wall waveguide via a mode converter which is realized by blind vias or through holes and provided between a planar line and the post-wall waveguide. According to the arrangement, a part of broad walls of the post-wall waveguide is replaced by a resistance film.
In the arrangement disclosed in Patent Literature 1, specifically, a microwave package has a plurality of metal patterns which serve as a multilayer substrate and are electrically connected with each other via an interlayer via. Between a lower metal pattern and a metal pattern above the lower metal, a pseudo-waveguide tube is formed which are defined by these metal patterns serving as a lower broad wall and an upper broad wall, respectively. On a metal pattern on a side of an upper surface of the microwave package, a microstrip line is provided via a dielectric layer. The microstrip line has one end thereof coupled with the pseudo-waveguide tube via a pseudo-coaxial line, a waveguide tube conversion section, and the like and the other end thereof connected with a microwave switch. A part of the lower broad wall for the pseudo-waveguide tube is constituted by a film resistor.
Accordingly, a microwave signal inputted to the microstrip line is guided to the pseudo-waveguide tube and converted into heat by the film resistor of the lower broad wall so at to be scattered and lost.